1. Forming Molecular Bonds
Covalent Bonding
Forming Molecular Bonds

2. What is a covalent bond? 7 valence e- 8 valence e-
The chemical bond that results from the sharing of electrons
Non-metals combine to acquire a full valence shell of 8 valence electrons
Example:
7 valence e-
8 valence e-

3. one atom takes e- from another
Degree of sharing
Non-polar Covalent
Polar Covalent
Ionic
e- are shared equally
e- shared unequally
one atom takes e- from another Na Cl e-

4. Types of covalent bonds
Single Covalent bonds- (also called sigma bonds) When a single pair of electrons is shared
Ex: H H
Group 7A: will form single covalent bonds
Group 6A: will form two single covalent bonds Ex: H2O
Group 5A: will form three single covalent bonds Ex: NH3- Ammonia
Group 4A: will form four single covalent bonds Ex: CH4- methane

5. Types of covalent bonds continued…
Multiple covalent bonds: Double or Triple bonds
Double covalent bond- when two pairs of electrons are shared.
Ex: O2 (draw lewis structure)
Triple covalent bond- formed when three pairs of electrons are shared between two atoms. Ex: N2 shares three pairs of electrons.
Pi bonds π- multiple bond consists of one sigma and one pi bond.
triple bond- one sigma and two pi bonds.
The shorter the bond the stronger the bond. Triple bonds are shorter.

6. Lewis dot structures : : : : : : 32 e- ex: CBr4 C = 4 16 prs
Rules for drawing dot structures:
Calculate the number of valence e- each atom
contributes. Divide this number in half to get
the number of pairs.
32 e-
ex: CBr4
C = 4
16 prs
Br = 7 x 4 = 28 6

7. : ex: CBr4 : Br : : : Br : C Br : : : Br : : :
3. Use pairs of e- (as single covalent bonds) to
attach all the other atoms to the center atom. :
ex: CBr4 : Br : : : Br : C Br : : : Br : : :
4. Put lone pairs of e- on the outside atoms until
each atom has 8 electrons (4 pairs) or 1 pair on
hydrogen.
5. Put any leftover pairs on the center atom so
that it also has 4 prs around it. 7

8. Lewis dot structures continued…
2. Decide which element will be the center at
usually the one that has fewer atoms or the
lower electronegativity
CH4
SO2
PCl5

9. Lewis dot structures continued…
How many valence electrons does it have? 4
How many hydrogens are there?
How many valence electrons do each have? 1
CH4
What is the central atom? C H H H
Now, join the electrons with a bond H
How many sigma bonds are there? 4

10. atoms share electrons in order to have 8 valence e- (2 for hydrogen)
diatomic elements H2 O2
Br2 F2 I2 N2
Cl2
Octet Rule:
atoms share electrons in order to have 8 valence e- (2 for hydrogen) 10

11. Naming Covalent Compounds
Covalent compounds are named by adding prefixes to the element names.
‘Covalent’ means both elements are nonmetals.
A prefix is added to the name of the first element in the formula ONLY if more than one atom of it is present.
A prefix is ALWAYS added to the name of the second element in the formula
The second element will use the form of its name ending in ‘ide’.

12. Naming Covalent Compounds
Prefixes
Subscript
Prefix 1
mono- 2
di- 3
tri- 4
tetra- 5
penta-
Subscript
Prefix 6
hexa- 7
hepta- 8
octa- 9
nona- 10
deca-
Note: When a prefix ending in ‘o’ or ‘a’ is added to ‘oxide’, the final vowel in the prefix is dropped.

13. Naming Binary Covalent Compounds: Examples1
mono 2 di 3
tri 4
tetra 5
penta 6
hexa 7
hepta 8
octa 9
nona 10
deca
* Second element ends ‘ide’
* Drop –a & -o before ‘oxide’
dinitrogen tetrasulfide
N2S4
NI3
nitrogen triiodide
XeF6
xenon hexafluoride
CCl4
carbon tetrachloride
P2O5
diphosphorus pentoxide
SO3
sulfur trioxide

14. Writing Chemical Formulas: A Review
I. Ionic Compounds
II. Covalent Compounds

15. Writing Formulas for Covalent Compounds
The names of covalent compounds contain prefixes that indicate the number of atoms of each element present.
First element:
if there is only one atom of that element in the formula (its subscript will be 1) and there should NOT be a prefix
Second element:
will ALWAYS have a prefix
will ALWAYS end in -ide
Remember:
Binary compounds contain only two elements, both of which are nonmetals
When in covalent compounds
atoms DO NOT have charges
Subscripts are determined directly from the prefixes in the
name.

16. Writing Formulas for Binary Covalent Compounds: Examples1
mono 2 di 3
tri 4
tetra 5
penta 6
hexa 7
hepta 8
octa 9
nona 10
deca
* Second element ends in ‘ide
* Drop –a & -o before ‘oxide’
nitrogen dioxide
NO2
diphosphorus pentoxide
P2O5
xenon tetrafluoride
XeF4
sulfur hexafluoride
SF6

17. Writing Formulas: Practice
carbon tetrafluoride
CF4
Writing Formulas: Practice
prefixes  covalent  prefixes indicate subscripts
sodium phosphate
Na3PO4
Analysis
If “Yes”
The compound is covalent: the prefixes give the subscripts.
* Are there prefixes present
The compound is ionic: subscripts must be determined by balancing charges
metal  ionic  balance charges  3 Na1+ needed for 1 PO43-
copper (I) sulfate
Cu2SO4
metal present  ionic  balance charges 2 Cu1+ needed for 1 SO42-
aluminum sulfide
Al2S3
metal present  ionic  balance charges 2 Al3+ needed for 3 S2-
dinitrogen pentoxide
N2O5
prefixes  covalent  prefixes indicate subscripts
ammonium nitrate
NH4NO3
polyatomic ion present  ionic  balance charges 
1 NH41+ needed for 1 NO31-
lead (IV) oxide
PbO2
metal present  ionic  balance charges 1 Pb4+ needed for 2 O2-
iron (III) carbonate
Fe2(CO3)3
metal present  ionic  balance charges 2 Fe3+ needed for 3 CO32-